Motor control device that decreases power consumed by control power source when power fails

ABSTRACT

A motor control device has a current value sampling unit configured to sample a current value of a motor, a PWM signal generation unit configured to generate a PWM signal to drive the motor, based on the sampled current value of the motor, and a power supply stop unit configured to stop supply of power from a control power supply to a peripheral depending on power stored in a DC link part and power to which the control power source can supply when an alternating-current power source fails.

RELATED APPLICATION DATA

This application claims priority under 35 U.S.C. §119 and/or §365 toJapanese Application No. 2012-142136 filed Jun. 25, 2012, the entirecontents of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a motor control device to which poweris supplied from a control power source configured to supply power to aperipheral of a motor in order to control the motor driven by powerstored in a DC link part connected to an alternating-current powersource via a converter.

2. Description of Related Art

A motor control device for controlling a motor in order to carry out atleast one of an operation to retract a driven object connected to themotor to a region where the driven object does not interfere with anobject and an operation to stop the motor in order to avoid interferenceof the driven object connected to the motor with the object when powerfails in a machine, such a machine tool, in which it is necessary tocarry out a synchronized operation of a work and a tool therein at alltimes, is proposed in, for example, Japanese Unexamined PatentPublication (Kokai) No. 8-54914 (JP8-54914A) and Japanese UnexaminedPatent Publication (Kokai) No. 2011-209936 (JP2011-209936A).

However, there may be a case where it is not possible to secure powernecessary for control by a motor control device to carry out at leastone of the operation to retract a driven object connected to a motor toa region where the driven object does not interfere with an object andthe operation to stop the motor in order to avoid interference of thedriven object connected to the motor with the object.

On the other hand, a control device that secures power of a controldevice when power fails by an uninterruptible power source device isproposed in, for example, Japanese Unexamined Patent Publication (Kokai)No. 5-333969 (JP5-333969A). However, the uninterruptible power sourcedevice is expensive, and therefore, if the uninterruptible power sourcedevice is used in order to secure power of the control device when powerfails, there is such a disadvantage that the system including thecontrol device is expensive.

Further, a motor control device that uses a control power source havinga smoothing capacitor in order to secure power of the motor controldevice when power fails without raising the cost of the system includingthe motor control device is proposed in, for example, JapaneseUnexamined Patent Publication (Kokai) No. 10-263973 (JP10-263973A) andJapanese Unexamined Patent Publication (Kokai) No. 2004-216829(JP2004-216829A).

However, power that the control power source having a smoothingcapacitor can secure when power fails is smaller than power that theuninterruptible power source device can secure. Consequently, in thecase where the control power source supplies power to a peripheral(motor cooling fan, monitor, etc.) of the motor in addition to the motorcontrol device, there may be a case where it is not possible to securepower necessary for the control by the motor control device to carry outat least one of the operation to retract a driven object connected tothe motor to a region where the driven object does not interfere with anobject and the operation to stop the motor in order to avoidinterference of the driven object connected to the motor with theobject.

Further, as a motor control device using a control power source having asmoothing capacitor, a motor control device that lengthens the outputhold time of the control power source by stopping supply of power to aperipheral of a motor in order to save parameters, operation values,etc. in a memory when power fails is proposed in, for example, JapaneseUnexamined Patent Publication (Kokai) No. 2007-185018 (JP2007-185018A).

The conventional motor control device that lengthens the output holdtime of the control power source when power fails in order to saveparameters, operation values, etc., in a memory when power fails isconfigured to stop supply of power to the peripheral of the motor evenif first power necessary to retract a driven object connected to themotor to a region where the driven object does not interfere with anobject, or second power necessary to stop the motor in order to avoidinterference of the driven object connected to the motor with theobject, or the sum of the first power and the second power cannot besecured, and therefore, it is not possible to lengthen the output holdtime of the control power source in order to make it possible to carryout at least one of the operation to retract the driven object connectedto the motor to a region where the driven object does not interfere withthe object and the operation to stop the motor in order to avoidinterference of the driven object connected to the motor with theobject.

SUMMARY OF THE INVENTION

As an aspect, the present invention provides a motor control devicecapable of lengthening the output hold time of a control power source inorder to make it possible to carry out at least one of the operation toretract a driven object connected to a motor to a region where thedriven object does not interfere with an object and the operation tostop the motor in order to avoid interference of the driven objectconnected to the motor with the object.

According to an aspect of the present invention, a motor control deviceto which power is supplied from a control power source configured tosupply power to a peripheral of a motor in order to control the motordriven by power stored in a DC link part connected to analternating-current power source via a converter, includes: a currentvalue sampling unit configured to sample a current value of the motor; aPWM signal generation unit configured to generate a PWM signal to drivethe motor, based on the sampled current value of the motor; and a powersupply stop unit configured to stop supply of power from the controlpower source to the peripheral depending on the power stored in the DClink part and power to which the control power source can supply whenthe alternating-current power source fails.

Preferably, the power supply stop unit stops the supply of power fromthe control power supply to the peripheral if the power stored in the DClink part is larger than any one of first power necessary to retract andriven object connected to the motor to a region where the driven objectdoes not interfere with an object, second power necessary to stop themotor in order to avoid interference of the driven object connected tothe motor with the object, and the sum of the first power and the secondpower, and the power to which the control power source can supply issmaller than the sum of power necessary to drive the peripheral andpower necessary to drive the motor control device when thealternating-current power source fails.

Preferably, the current value sampling unit increases a sampling periodof the current value of the motor if the power stored in the DC linkpart is larger than any one of the first power, the second power, andthe sum of the first power and the second power, and the power to whichthe control power source can supply is smaller than the power necessaryto drive the motor control device when the alternating-current powersource fails.

Preferably, the PWM signal generation unit increases a carrier frequencyof the PWM signal if the power stored in the DC link part is larger thanany one of the first power, the second power, and the sum of the firstpower and the second power, and the power to which the control powersource can supply is smaller than the power necessary to drive the motorcontrol device when the alternating-current power source fails.

Preferably, the motor control device further has a motor sampling unitconfigured to sample the position or speed of the motor, a driven objectsampling unit configured to sample the position or speed of the drivenobject connected to the motor, and an operation stop unit configured tostop the operation of any one of the motor sampling unit and the drivenobject sampling unit if the power stored in the DC link part is largerthan any one of the first power, the second power, and the sum of thefirst power and the second power, and the power to which the controlpower supply can supply is smaller than the power necessary to drive themotor control device when the alternating-current power source fails.

Preferably, the power supply stop unit stops the supply of power fromthe control power source to the peripheral if the power stored in the DClink part is equal to or less than first power necessary to retract thedriven object connected to the motor to a region where the driven objectdoes not interfere with the object and at the same time, is larger thansecond power necessary to stop another motor in order to avoidinterference of a driven object connected to the other motor connectedin parallel to the motor controlled by the motor control device with anobject, the sum of the power stored in the DC link part and reductionenergy stored in the DC link part while the other motor is coming to astop is larger than the sum of the first power and the second power, andthe power to which the control power source can supply is smaller thanthe sum of the power necessary to drive the peripheral and the powernecessary to drive the motor control device and the motor control deviceof the other motor when the alternating-current power source fails.

Preferably, the current value sampling unit increases the samplingperiod of the current value of the motor if the power stored in the DClink part is equal to or less than the first power and at the same time,is larger than the second power, the sum of the power stored in the DClink part and the reduction energy generated while another motor iscoming to a stop is larger than the sum of the first power and thesecond power, and the power to which the control power source can supplyis smaller than the power necessary to drive the motor control deviceand the motor control device of the other motor when thealternating-current power source fails.

Preferably, the PWM signal generation unit increases the carrierfrequency of the PWM signal if the power stored in the DC link part isequal to or less than the first power and at the same time, is largerthan the second power, the sum of the power stored in the DC link partand the reduction energy generated while another motor is coming to astop is larger than the sum of the first power and the second power, andthe power that the control power source can supply is smaller than thepower necessary to drive the motor control device and the motor controldevice of the other motor when the alternating-current power sourcefails.

Preferably, the motor control device further has a motor sampling unitconfigured to sample the position or speed of the motor, a driven objectsampling unit configured to sample the position or speed of the drivenobject connected to the motor, and an operation stop unit configured tostop the operation of any one of the motor sampling unit and the drivenobject sampling unit if the power stored in the DC link part is equal toor less than the first power and at the same time, is larger than thesecond power, the sum of the power stored in the DC link part and thereduction energy generated while another motor is coming to a stop islarger than the sum of the first power and the second power, and thepower to which the control power source can supply is smaller than thepower necessary to drive the motor drive device and the motor controldevice of the other motor when the alternating-current power sourcefails.

According to the motor control device of an aspect of the presentinvention, it is possible to lengthen the output hold time of thecontrol power source in order to make it possible to carry out at leastone of the operation to retract the driven object connected to the motorto a region where the driven object does not interfere with the objectand the operation to stop the motor in order to avoid interference ofthe driven object connected to the motor with the object.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features, and advantages of the present invention will beclear based on the description in the following embodiments relating tothe accompanying drawings. In the drawings,

FIG. 1 is a block diagram of a system having a motor control device ofan embodiment of the present invention;

FIG. 2 is a block diagram of the motor control device in FIG. 1;

FIG. 3 is a flowchart of an operation of an upper control device in FIG.1;

FIG. 4 is a block diagram of another system having the motor controldevice according to an embodiment of the present invention; and

FIG. 5 is a flowchart of an operation of an upper control device in FIG.4.

DETAILED DESCRIPTION

Embodiments of the present invention are explained with reference to thedrawings. In the drawings, the same symbols are attached to the samecomponents.

Referring to the drawings, FIG. 1 is a block diagram of a system havinga motor control device of an embodiment of the present invention andFIG. 2 is a block diagram of the motor control device in FIG. 1. Thesystem shown in FIG. 1 is used in a machine tool, in which it isnecessary to carry out a synchronized operation of a work and a tooltherein at all times. The system shown in FIG. 1 has a three-phasealternating-current power source 1 as an alternating-current powersource, a converter 2, a smoothing capacitor 3 as a DC link part, aninverter 4, a motor 5, a driven object 6, rotation angle detection units7 and 8, a memory 9, a motor control device 10, a control power source11, a monitor 12 as a peripheral, a cooling fan 13 as the peripheral,switches 14 and 15, a power failure detection unit 16, an upper controldevice 17, and a switch 18.

The converter 2 consists of, for example, a plurality (six, in the caseof three-phase alternating current) of rectifier diodes and convertsalternating-current power supplied from the three-phasealternating-current power source 1 into direct-current power. Thesmoothing capacitor 3 is connected in parallel to the converter 2 inorder to smooth a voltage rectified by the rectifier diode of theconverter 2. The inverter 4 is connected in parallel to the smoothingcapacitor 3, consists of, for example, a plurality (six, in the case ofthree-phase alternating current) of rectifier diodes and transistorsconnected in inverse parallel to the rectifier diodes, respectively, andconverts the direct-current power into which converted by the converter2 into alternating-current power by turning on and off the transistorbased on a PWM signal V_(PWM), to be explained later.

The motor 5 is driven by power stored in the smoothing capacitor 3. Asthe motor 5, a gravity axis servo motor configured to drive the mainaxis of a machine tool in the gravity axis direction (Z-axis direction)by a feed screw mechanism, such as a ball screw and nut mechanism, amain axis motor configured to drive a tool attached to the main axis ofa machine tool, a horizontal axis serve motor configured to drive atable of a machine tool to which a work is attached in the horizontaldirection (for example, X-axis direction) by a feed screw mechanism,such as a ball screw and nut mechanism, etc., is used.

The driven object 6 is, for example, the main axis of a machine tool inthe case where the motor 5 is a gravity axis servo motor, or a tool inthe case where the motor 5 is a main axis motor, or a table of a machinetool in the case where the motor 5 is a horizontal axis servo motor.

The rotation angle detection unit 7 consists of a rotary encoderconfigured to detect a rotation angle θ₁ of the motor 5 as the positionof the motor, and the rotation angle detection unit 8 consists of arotary encoder configured to detect a rotation angle θ₂ of the drivenobject 6 as the position of the driven object.

The memory 9 stores a lookup table indicating a relationship among arotation speed command value ω_(com), which is a speed command value forthe motor 5 to be input to the motor control device 10 from the uppercontrol device 17, an actual rotation speed ω of the motor 5corresponding to the position or speed of the motor 5, to be calculatedas will be explained later, a q-axis current command value I_(qcom), anda d-axis current command value I_(dcom).

The motor control device 10 controls the motor 5 driven by power storedin the smoothing capacitor 3 connected to the three-phasealternating-current power source 1 via the converter 2. To do this, themotor control device 10 samples each of current values of three phasesof a U-phase current I_(U), a V-phase current I_(V), and a W-phasecurrent I_(W) detected by current detection units 4 u, 4 v, and 4 wprovided in output lines of the inverter 4 as the current value of themotor 5, and samples each of the rotation angles θ₁ and θ₂ as theposition or speed of the motor and the position or speed of the drivenobject. Then, the motor control device 10 generates the PWM signalV_(PWM) to drive the motor 5, based on each of the sampled currentvalues of the U-phase current I_(U), the V-phase current I_(V), and theW-phase current I_(W), and the sampled rotation angles θ₁ and θ₂. Thecurrent detection units 4 u, 4 v, and 4 w consist of, for example, holeelements. In order to control the motor 5, power is supplied from thecontrol power source 11, which is configured to supply power to themonitor 12 and the cooling fan 13, to the motor control device 10.

Further, the motor control device 10 carries out the control to lengthenthe output hold time of the control power source 11 in order to make itpossible to carry out at least one of the operation to retract thedriven object 6 (for example, tool) to a region where driven object 6does not interfere with an object (for example, work attached to thetable of the machine tool) and the operation to safely stop the motor 5in order to avoid interference of the driven object 6 with the object(i.e., operation to stop motor 5 by reducing the rotation speed commandvalue ω_(com) to zero in order to avoid interference of the drivenobject 6 with the object caused by the movement (for example, fall) ofthe motor 5) when the three-phase alternating-current power source 1fails.

In order to carry out the control of the motor 5 and control to lengthenthe output hold time of the control power source 11, the motor controldevice 10 has a current value sampling unit 10 a, a motor sampling unit10 b, a driven object sampling unit 10 c, a subtracter 10 d, a filter 10e, an adder 10 f, a q-axis current command value creation unit 10 g, ad-axis current command value creation unit 10 h, a subtracter 10 i, asubtracter 10 j, a PI control unit 10 k, a PI control unit 101, acommand voltage creation unit 10 m, a PWM signal generation unit 10 n, apower supply stop unit 10 o, and an operation stop unit 10 p.

The current value sampling unit 10 a samples the current values of thethree phases of the U-phase current I_(U), the V-phase current I_(V),and the W-phase current I_(W) flowing through the motor 5 at eachsampling period (control period of the motor control device 10)corresponding to a one clock period (for example, 250 microseconds) of aclock signal, which is output to each unit of the motor control device10 by a clock (not shown schematically) incorporated in the motorcontrol device 10, and detects a q-axis current I_(q) and a d-axiscurrent I_(q), based on the three phases of the U-phase current I_(U),the V-phase current I_(V), and the W-phase current I_(W) flowing throughthe motor 5 and a rotation angle θ corresponding to the actual rotationspeed ω of the motor 5. To do this, the current value sampling unit 10 aconsists of a coordinate converter configured to perform rotationcoordinate conversion and three-phase to two-phase conversion.Consequently, the current value sampling unit 10 a converts the threephases of the U-phase current I_(U), the V-phase current I_(V), and theW-phase current I_(W) in the stationary coordinate system (UVWcoordinate system) into two phases of the q-axis current I_(q) and thed-axis current I_(d) expressed by the rotation coordinate system rotatedby the rotation angle θ corresponding to the actual rotation speed ωwith respect to the stationary coordinate system (αβ coordinate system),and outputs the q-axis current I_(q) and the d-axis current I_(d) to thesubtracter 10 i and the subtracter 10 j, respectively.

In this case, the three phases of the U-phase current I_(U), the V-phasecurrent I_(V), and the W-phase current I_(W) are detected by the currentdetection units 4 u, 4 v, and 4 w provided in the output lines of theinverter 4 and current detection signals, which is output from thecurrent detection units 4 u, 4 v, and 4 w, are input to an A/Dconverter, not shown schematically, and converted into digital data. Thecurrent detection units 4 u, 4 v, and 4 w are consist of, for example,hole elements.

In the motor control device 10 shown in FIG. 2, the current valuesampling unit 10 a increases the sampling period of the current valuesof the U-phase current I_(U), the V-phase current I_(V), and the W-phasecurrent I_(W) in such a manner as will be described later in detail if asampling period increase command C_(s), described later, is input fromthe upper control device 17.

The motor sampling unit 10 b samples the rotation angle θ₁ at eachsampling period described above, and differentiates the rotation angleθ₁ with respect to time to calculate a rotation speed ω₁ of the motor 5corresponding to the frequency of the U-phase current I_(U), the V-phasecurrent I_(V), and the W-phase current I_(W), and outputs the rotationspeed ω₁ to the subtracter 10 d and the adder 10 f.

In the motor control device 10 shown in FIG. 2, the motor sampling unit10 b increases the sampling period of the rotation angle θ₁ in such amanner as will be explained later in detail if the above-mentionedsampling period increase command C_(s) is input from the upper controldevice 17.

The driven object sampling unit 10 c is provided to carry outfull-closed control. To do this, the driven object sampling unit 10 csamples the rotation angle θ₂ at each sampling period described above,differentiates the rotation speed θ₂ with respect to time to calculate arotation speed χ₂ of the driven object 6 corresponding to the frequencyof the U-phase current I_(U), the V-phase current I_(V), and the W-phasecurrent I_(W), as the speed of the driven object 6, and outputs therotation speed ω₂ to the subtracter 10 d.

In the motor control device 10 shown in FIG. 2, the driven objectsampling unit 10 c increases the sampling period in such a manner aswill be explained later in detail if the above-mentioned sampling periodincrease command C_(s) is input from the upper control device 17.Further, the driven object sampling unit 10 c operates while the switch18 is on and stops the operation thereof while the switch 18 is off.

The subtracter 10 d has a non-inversion input part to which the rotationspeed ω₁ of the motor 5 is input, an inversion input part to which therotation speed ω₂ of the driven object 6 is input, and an output partconfigured to output a difference Δω₁, which is a result of subtractionbetween the rotation speed ω₁ of the motor 5 and the rotation speed ω₂of the driven object 6, to the filter 10 e. The filter 10 e filters thedifference Δω₁ and outputs the filtered difference Δω₂ to the adder 10f. The adder 10 f has a first non-inversion input part to which therotation speed ω₁ of the motor 5 is input, a second non-inversion inputpart to which the filtered difference Δω₂ is input, and an output partconfigured to output the rotation speed ω of the motor, which is aresult of addition of the rotation speed ω₁ of the motor 5 and thefiltered difference Δω₂, to the q-axis current command value creationunit 10 g and the d-axis current command value creation unit 10 h.

The q-axis current command value creation unit 10 g creates the q-axiscurrent command value I_(qcom). To do this, the actual rotation speed ωof the motor 5 is input from the adder 10 f to the q-axis currentcommand value creation unit 10 g, the rotation speed command valueω_(com) is input from the upper control device 17 to the q-axis currentcommand value creation unit 10 g, the q-axis current command valuecreation unit 10 g reads the q-axis current command value I_(qcom),which corresponds to the rotation speed command value ω_(com) and theactual rotation speed ω of the motor 5, from the memory 9, and theq-axis current command value creation unit 10 g outputs the read q-axiscurrent command value I_(qcom) to the subtracter 10 i.

The d-axis current command value creation unit 10 h creates the d-axiscurrent command value I_(dcom). To do this, the actual rotation speed ωof the motor 5 is input from the adder 10 f to the d-axis currentcommand value creation unit 10 h, the rotation speed command valueω_(com) is input from the upper control device 17 to the d-axis currentcommand value creation unit 10 h, the d-axis current command valuecreation unit 10 h reads the d-axis current command value I_(dcom),which corresponds to the rotation speed command value ω_(com) and theactual rotation speed ω of the motor 5, from the memory 9 and the d-axiscurrent command value creation unit 10 h outputs the read d-axis currentcommand value I_(dcom) to the subtracter 10 j.

The subtracter 10 i has a non-inversion input part to which the q-axiscurrent command value I_(qcom) is input, an inversion input part towhich the q-axis current I_(q) is input, and an output part configuredto output a current deviation ΔI_(q), which is a result of subtractionbetween the q-axis current command value I_(qcom) and the value of theq-axis current I_(q). The subtracter 10 j has a non-inversion input partto which the d-axis current command value I_(dcom) is input, aninversion input part to which the d-axis current I_(d) is input, and anoutput part configured to output a current deviation ΔI_(d), which is aresult of subtraction between the d-axis current command value I_(dcom)and the value of the d-axis current I_(d).

The current deviation ΔI_(q) is input to the PI control unit 10 k, thePI control unit 10 k creates a q-axis voltage command value V_(q) bymaking proportional integral calculation of the current deviationΔI_(q), and the PI control unit 10 k outputs the q-axis voltage commandvalue V_(q) to the command voltage creation unit 10 m. The currentdeviation ΔI_(d) is input to the PI control unit 101, the PI controlunit 101 creates a d-axis voltage command value V_(d) by makingproportional integral calculation of the current deviation ΔI_(d), andthe PI control unit 101 outputs the d-axis voltage command value V_(d)to the command voltage creation unit 10 m.

The command voltage creation unit 10 m creates a U-phase voltage commandvalue V_(U), a V-phase voltage command value V_(V), and a W-phasevoltage command value V_(W), based on the q-axis voltage command valueV_(q) and the d-axis voltage command value V_(d). To do this, thecommand voltage creation unit 10 m consists of a coordinate converterconfigured to perform rotation coordinate conversion and two-phase tothree-phase conversion. Consequently, the command voltage creation unit10 m converts the two phases of the d-axis voltage command value V_(d)and the q-axis voltage command value V_(q) expressed by the rotationcoordinate system rotated by the rotation angle θ corresponding to theactual rotation speed ω of the motor 5 with respect to the stationarycoordinate system (αβ coordinate system) into three phases of theU-phase voltage command value V_(U), the V-phase voltage command valueV_(V), and the W-phase voltage command value V_(W), and outputs theU-phase voltage command value V_(U), the V-phase voltage command valueV_(V), and the W-phase voltage command value V_(W) to the PWM signalgeneration unit 10 n.

The PWM signal generation unit 10 n generates the PWM signal V_(PWM) (inthis case, V_(PWM1), V_(PWM2), V_(PWM3), V_(PWM4), V_(PWM5), andV_(PWM6) corresponding to each transistor of the converter 4), based onthe U-phase voltage command value V_(U), the V-phase voltage commandvalue V_(V), and the W-phase voltage command value V_(W), i.e., thesampled current values of the three phases of the U-phase current I_(U),the V-phase current I_(V), and the W-phase current I_(W), and thesampled rotation angles θ₁ and θ₂, and outputs the PWM signal V_(PWM) inorder to drive the motor 5. To do this, the PWM signal generation unit10 n generates the PWM signal V_(PWM), based on the carrier frequencycorresponding to one period (for example, 250 microseconds) of a timer(not shown schematically) incorporated in the motor control device 10.

In the motor control device 10 shown in FIG. 2, the PWM signalgeneration unit 10 n increases the carrier frequency in such a manner aswill be explained later in detail if a carrier frequency increasecommand C_(g), to be explained later, is input from the upper controldevice 17.

If a power supply stop command C_(p), to be explained later, is inputfrom the upper control device 17 to the power supply stop unit 10 o, thepower supply stop unit 10 o supplies a switching signal S_(off) to turnoff the switches 14 and 15 to the switches 14 and 15, and if the powersupply stop command C_(p) is not input from the upper control unit 17 tothe power supply stop unit 10 o while the motor 5 is being driven, thepower supply stop unit 10 o supplies a switching signal S_(on) to turnon the switches 14 and 15 to the switches 14 and 15.

If an operation stop command C_(o), to be explained later, is input fromthe upper control device 17 to the operation stop unit 10 p, theoperation stop unit 10 p supplies a switching signal S_(off)′ to turnoff the switch 18 to the switch 18, and if the operation stop commandC_(o) is not input from the upper control device 17 to the operationstop unit 10 p while the motor 5 is being driven, the operation stopunit 10 p supplies a switching signal S_(on)′ to turn on the switch 18to the switch 18.

The control power source 11 supplies power to the motor control device10, the monitor 12, and the cooling fan 13. To do this, the controlpower source 11 has a converter 11 a, a smoothing capacitor 11 b, and aninverter 11 c.

The converter 11 a consists of, for example, a plurality (two, in thiscase) of rectifier diodes and converts alternating-current powersupplied from the three-phase alternating-current power source 1 intodirect-current power. The smoothing capacitor 11 b has a capacitancesmaller than the capacitance of the smoothing capacitor 3 and isconnected in parallel to the converter 11 a in order to smooth a voltagerectified by the rectifier diode of the converter 11 a. The inverter 11c is connected in parallel to the smoothing capacitor 11 b and consistsof, for example, a plurality (two, in this case) of rectifier diodes andtransistors connected in inverse parallel to the rectifier diodes,respectively, and converts the direct-current power into which convertedby the converter 11 a into alternating-current power by turning on andoff the transistors.

The monitor 12 displays various kinds of information, and power issupplied from the control power source 11 to the monitor 12. The coolingfan 13 cools down the motor 5 and the motor control device 10, and poweris supplied from the control power source 11 to the cooling fan 13. Theswitch 14 turns on in response to the switching signal S_(on) from thepower supply stop unit 10 o in order to supply power from the controlpower source 11 to the monitor 12, and turns off in response to theswitching signal S_(off) from the power supply stop unit 10 o in orderto stop the supply of power from the control power source 11 to themonitor 12. The switch 15 turns on in response to the switching signalS_(on) from the power supply stop unit 10 o in order to supply powerfrom the control power source 11 to the cooling fan 13, and turns off inresponse to the switching signal S_(off) from the power supply stop unit10 o in order to stop the supply of power from the control power source11 to the cooling fan 13.

The power failure detection unit 16 detects a power failure of thethree-phase alternating-current power source 1. To do this, the powerfailure detection unit 16 has a rectifier circuit (not shownschematically) having a plurality (six, in the case of three-phasealternating current) of rectifier diodes configured to rectify threephases of a U-phase current i_(U), a V-phase current i_(V), and aW-phase current i_(W) detected by current detection units 1 u, 1 v, and1 w provided in the output lines of the three-phase alternating-currentpower source 1, and a comparator (not shown schematically) configured tocompare the level of an output signal from the rectifier circuit and thereference level and to output a power failure detection signal S_(s) tothe upper control device 17 if the level of the output signal is lowerthan the reference level. The current detection units 1 u, 1 v, and 1 wconsist of, for example, hole elements.

In the system shown in FIG. 1, the memory 9, the motor control device10, and the power failure detection unit 16 are implemented by aprocessor including an input/output port, a serial communicationcircuit, an A/D converter, a comparator, etc., and processing, to beexplained later, is performed in accordance with processing programsstored in a memory, not shown schematically.

The upper control device 17 consists of a CNC (computer numericalcontrol), etc., and inputs the rotation speed command value ω_(com) tothe q-axis current command value creation unit 10 g and the d-axiscurrent command value creation unit 10 h in order to control the motorcontrol device 10. Further, when the power failure detection signalS_(s) is input, the upper control device 17 detects a voltage (DC linkvoltage) V_(c1) of the smoothing capacitor 3 and a voltage V_(c2) of thesmoothing capacitor 11 b. Then, the upper control device 17 calculatesmotor power source suppliable power P_(m) stored in the smoothingcapacitor 3 and power stored in the smoothing capacitor 11 b, i.e.,control power source suppliable power P_(c) to which the control powersource 11 can supply when the alternating-current power source 1 fails,respectively, based on the detected voltage V_(c1) and the voltageV_(c2).

The switch 18 turns on in response to the switching signal S_(on)′ fromthe operation stop unit 10 p in order to supply the rotation angle θ₂from the rotation angle detection unit 8 to the driven object samplingunit 10 c, and turns off in response to the switching signal S_(off)′from the operation stop unit 10 p in order to stop the supply of therotation angle θ₂ from the rotation angle detection unit 8 to the drivenobject sampling unit 10 c.

In the system shown in FIG. 1, motor drive power P_(sr) corresponding toany one of the first power necessary to retract the driven object 6 to aregion where the driven object 6 does not interfere with an object, thesecond power necessary to stop the motor 5 in order to avoidinterference of the driven object 6 with an object when thealternating-current power source 1 fails, and the sum of the first powerand the second power is stored in association with the rotation speedcommand value ω_(com) in a memory (not shown schematically) of the uppercontrol device 17 in advance. Further, peripheral drive power P_(mf)necessary to drive the monitor 12 and the cooling fan 13 when thealternating-current power source 1 fails is stored in the memory (notshown schematically) of the upper control device 17 in advance.Furthermore, first motor control device drive power P_(mc1) necessary todrive the motor control device 10 when the alternating-current powersource 1 fails, second motor control device drive power P_(mc2)necessary to drive the motor control device 10 at the time of increasingthe above-mentioned sampling period when the alternating-current powersource 1 fails, and third motor control device drive power P_(mc3)necessary to drive the motor control device 10 at the time of increasingthe sampling period and the carrier frequency when thealternating-current power source 1 fails are stored in association withthe rotation speed command value ω_(com) in the memory (not shownschematically) of the upper control device 17 in advance.

If the motor power source suppliable power P_(m) is larger than themotor drive power P_(sr) and the control power source suppliable powerP_(c) is smaller than the sum of the peripheral drive power P_(mf) andthe first motor control device drive power P_(mc1) when the uppercontrol device 17 receives the power failure detection signal S_(s), theupper control device 17 outputs the power supply stop command C_(p) tostop the supply of power from the control power source 11 to the monitor12 and the cooling fan 13 to the power supply stop unit 10 o.

If the motor power source suppliable power P_(m) is larger than themotor drive power P_(sr) and the control power source suppliable powerP_(c) is smaller than the first motor control device drive power P_(mc1)when the upper control device 17 receives the power failure detectionsignal S_(s), the upper control device 17 outputs the sampling periodincrease command C_(s) to increase the above-mentioned sampling period(for example, to double the sampling period) to the current valuesampling unit 10 a, the motor sampling unit 10 b, and the drive objectsampling unit 10 c, respectively.

If the motor power source suppliable power P_(m) is larger than themotor drive power P_(sr) and the control power source suppliable powerP_(c) is smaller than the second motor control device drive powerP_(mc2) when the upper control device 17 receives the power failuredetection signal S_(s), the upper control device 17 outputs the carrierfrequency increase command C_(g) to increase the above-mentioned carrierfrequency (for example, to double the carrier frequency) to the PWMsignal generation unit 10 n.

If the motor power source suppliable power P_(m) is larger than themotor drive power P_(sr) and the control power source suppliable powerP_(c) is smaller than the third motor control device drive power P_(mc3)when the upper control device 17 receives the power failure detectionsignal S_(s), the upper control device 17 outputs the operation stopcommand C_(o) to stop the operation of the driven object sampling unit10 c to the operation stop unit 10 p.

FIG. 3 is a flowchart of the operation of the upper control device inFIG. 1, which is performed at each control period (for example, 250microseconds) during the period from the start of the drive of the motor5 to the end of the drive of the motor 5 or the detection of the powerfailure of the three-phase alternating-current power source 1, and iscontrolled by the processing program executed in the upper controldevice 17.

First, the upper control device 17 determines whether or not it receivesthe power failure detection signal S_(s) (step S1). If the upper controldevice 17 does not receive the power failure detection signal S_(s), theprocessing flow is exited. In contrast, if the upper control device 17receives the power failure detection signal S_(s), the upper controldevice 17 calculates the motor power source suppliable power P_(m) andthe control power source suppliable power P_(c) (step S2).

After step S2 is completed, the upper control device 17 determineswhether or not the motor power source suppliable power P_(m) is largerthan the motor drive power P_(sr) (step S3). If the motor power sourcesuppliable power P_(m) is equal to or less than the motor drive powerP_(sr), the processing flow is exited. In contrast, if the motor powersource suppliable power P_(m) is larger than the motor drive powerP_(sr), the upper control device 17 determines whether or not thecontrol power source suppliable power P_(c) is equal to or more than thesum of the peripheral drive power P_(mf) and the first motor controldevice drive power P_(mc1) (step S4).

If the control power source suppliable power P_(c) is equal to or morethan the sum of the peripheral drive power P_(mf) and the first motorcontrol device drive power P_(mc1), the processing flow is exited. Incontrast, if the control power source suppliable power P_(c) is smallerthan the sum of the peripheral drive power P_(mf) and the first motorcontrol device drive power P_(mc1), the upper control device 17 outputsthe power supply stop command C_(p) to the power supply stop unit 10 o(step S5).

After step S5 is completed, the upper control device 17 determineswhether or not the control power source suppliable power P_(c) is equalto or more than the first motor control device drive power P_(mc1) (stepS6). If the control power source suppliable power P_(c) is equal to ormore than the first motor control device drive power P_(mc1), theprocessing flow is exited. In contrast, if the control power sourcesuppliable power P_(c) is smaller than the first motor control devicedrive power P_(mc1), the upper control device 17 outputs the samplingperiod increase command C_(s) to the current value sampling unit 10 a,the motor sampling unit 10 b, and the driven object sampling unit 10 c,respectively (step S7).

If the sampling period increase command C_(s) is input from the uppercontrol device 17 to the current value sampling unit 10 a, the motorsampling unit 10 b and the driven object sampling unit 10 c, theyperform sampling processing each time they receive the clock signaltwice, which is output from a clock (not shown schematically)incorporated in the motor control device 10. Consequently, the currentvalue sampling unit 10 a, the motor sampling unit 10 b, and the drivenobject sampling unit 10 c each perform the sampling processing at eachsampling period (control period of the motor control device 10)corresponding to the two clock periods (for example, 500 microseconds).That is, the sampling period of the current value sampling unit 10 a,the motor sampling unit 10 b and the driven object sampling unit 10 cincrease to a sampling period twice that before the sampling periodincrease command C_(s) is input.

The control period of the motor control device 10 corresponding to thesampling period of the current value sampling unit 10 a, the motorsampling unit 10 b and the driven object sampling unit 10 c consists ofa processing period of time during which each unit of the motor controldevice 10 performs processing and a rest period of time during whicheach unit of the motor control device 10 is at rest. The processingperiod of time is constant regardless of the length of the controlperiod of the motor control device 10, and the power consumed by themotor control device 10 during the processing period of time is largerthan the power consumed by the motor control device 10 during the restperiod of time. Consequently, the power consumed by the motor controldevice 10 decreases as the ratio of the processing period of time to thelength of the control period of the motor control device 10 decreases.According to the present embodiment, by increasing the sampling periodof the current value sampling unit 10 a, the motor sampling unit 10 b,and the driven object sampling unit 10 c, the ratio of the processingperiod of time to the length of the control period of the motor controldevice 10 decreases, and therefore, it is possible to decrease the powerconsumed by the motor control device 10.

After step S7 is completed, the upper control device 17 determineswhether or not the control power source suppliable power P_(c) is equalto or more than the second motor control device drive power P_(mc2)(step S8). If the control power source suppliable power P_(c) is equalto or more than the second motor control device drive power P_(mc2), theprocessing flow is exited. In contrast, if the control power sourcesuppliable power P_(c) is smaller than the second motor control devicedrive power P_(mc2), the upper control device 17 outputs the carrierfrequency increase command C_(g) to the PWM signal generation unit 10 n(step S9).

If the carrier frequency increase command C_(g) is input from the uppercontrol device 17 to the PWM signal generation unit 10 n, the PWM signalgeneration unit 10 n sets a carrier frequency corresponding to twoperiods (for example, 500 microseconds) of a timer (not shownschematically) incorporated in the motor control device 10, andgenerates the PWM signal V_(PWM) based the set carrier frequency.Consequently, the carrier frequency increases to a carrier frequencytwice that before the carrier frequency increase command C_(g) is input.

The number of times the PWM signal V_(PWM) is generated per unit time(for example, one second) decreases as the carrier frequency increases,and the power necessary for the PWM signal generation unit 10 n togenerate the PWM signal V_(PWM) decreases as the number of times the PWMsignal V_(PWM) is generated per unit time (for example, one second)decreases. According to the present embodiment, by increasing thecarrier frequency, the number of times the PWM signal V_(PWM) isgenerated per unit time (for example, one second) decreases, andtherefore, it is possible to decrease the power consumed by the motorcontrol device 10.

After step S9 is completed, the upper control device 17 determineswhether or not the control power source suppliable power P_(c) is equalto or more than the third motor control device drive power P_(mc3) (stepS10). If the control power source suppliable power P_(c) is equal to ormore than the third motor control device drive power P_(mc3), theprocessing flow is exited. In contrast, if the control power sourcesuppliable power P_(c) is smaller than the third motor control devicedrive power P_(mc3), the upper control device 17 outputs the operationstop command C_(o) to the operation stop unit 10 p (step S11) and exitsthe processing flow.

If the operation stop command C_(o) is input from the upper controldevice 17 to the operation stop unit 10 p, the operation stop unit 10 psupplies the switching signal S_(off)′ to the switch 18. Consequently,the driven object sampling unit 10 c stops the operation thereof andpower is no longer consumed by the driven object sampling unit 10 c, andtherefore, it is possible to decrease the power consumed by the motorcontrol device 10.

In the case where the motor 5 is a gravity axis servo motor, the motorcontrol device 10 carries out the control of the motor 5 to retract thedriven object 6 to a region where the driven object 6 does not interferewith an object and to stop the motor 5 in order to avoid interference ofthe driven object 6 with an object when the processing flow in FIG. 3 ofthe upper control device 17 is exited. In the case where the motor 5 isa horizontal axis servo motor, the motor control device 10 carries outthe control of the motor 5 to retract the driven object to a regionwhere the driven object 6 does not interfere with an object when theprocessing flow in FIG. 3 of the upper control device 17 is exited. Inthe case where the motor 5 is a main axis motor, the motor controldevice 10 carries out the control of the motor 5 to stop the motor 5 inorder to avoid interference of the driven object 6 with an object whenthe processing flow in FIG. 3 of the upper control device 17 is exited.

According to the system shown in FIG. 1, the supply of power from thecontrol power source 11 to the monitor 11 and the cooling fan 13 isstopped if the motor power source suppliable power P_(m) is larger thanthe motor drive power P_(s), and the control power source suppliablepower P_(c) is smaller than the sum of the peripheral drive power P_(mf)and the first motor control device drive power P_(mc1) when thethree-phase alternating-current power source 1 fails, and therefore, itis possible to decrease the power consumed by the motor control device10. Consequently, it is possible to lengthen the output hold time of thecontrol power source 11 without increasing the capacitance of thesmoothing capacitor 11 b in order to make it possible to carry out atleast one of the operation to retract the driven object 6 to a regionwhere the driven object 6 does not interfere with an object and theoperation to stop the motor 5 in order to avoid interference of thedriven object 6 with an object when the three-phase alternating-currentpower source 1 fails.

Further, if the motor power source suppliable power P_(m) is larger thanthe motor drive power P_(sr) and the control power source suppliablepower P_(c) is smaller than the first motor control device drive powerP_(mc1), the second motor control device drive power P_(mc2) or thethird motor control device drive power P_(mc3) when the three-phasealternating-current power source 1 fails, it is possible to furtherdecrease the power consumed by the motor control device 10 by increasingthe sampling period of the current value sampling unit 10 a, the motorsampling unit 10 b, and the driven object sampling unit 10 c, byincreasing both the sampling period of the current value sampling unit10 a, the motor sampling unit 10 b and the driven object sampling unit10 c and the carrier frequency of the PWM signal V_(PWM), or by stoppingthe operation of the driven object sampling unit 10 c.

FIG. 4 is a block diagram of another system having the motor controldevice according to the embodiment of the present invention. The systemshown in FIG. 4 is used in a machine tool, in which it is necessary tocarry out a synchronized operation of a work and a tool therein at alltimes. The system shown in FIG. 4 has an upper control device 17′ inplace of the upper control device 17 in FIG. 1 and, in addition to thecomponents of the system shown in FIG. 1 other than the upper controldevice 17, the system has an inverter 4′, a motor 5′, a driven object6′, rotation angle detection units 7′ and 8′, a memory 9′, and a motorcontrol device 10′.

The inverter 4′ is connected in parallel to the smoothing capacitor 3and the motor 5 and consists, for example, of a plurality (six, in thecase of three-phase alternating current) of rectifier diodes andtransistors connected in inverse parallel to the rectifier diodes,respectively, and converts the direct-current power into which convertedby the converter 2 into alternating-current power by turning on and offthe transistors based on a PWM signal V_(PWM)′, to be explained later.

The motor 5′ is driven by power stored in the smoothing capacitor 3. Inthe system shown in FIG. 4, as the motor 5, for example, a firsthorizontal axis servo motor configured to drive a table of a machinetool to which a work is attached in a first horizontal direction (forexample, X-axis direction) by a feed screw mechanism, such as a ballscrew and nut mechanism, is used, and as the motor 5′, for example, asecond horizontal axis servo motor configured to drive a table of amachine tool to which a work is attached in a second horizontaldirection (for example, Y-axis direction) orthogonal to the firsthorizontal direction by a feed screw mechanism, such as a ball screw andnut mechanism, is used.

The driven object 6 and the driven object 6′ are, for example, tables ofthe same machine tool in the case where the motors 5 and 5′ are thefirst horizontal axis servo motor and the second horizontal axis servomotor, respectively.

The rotation angle detection unit 7′ consists of a rotary encoderconfigured to detect a rotation angle θ₁′ of the motor 5′ as theposition of the motor, and the rotation angle detection unit 8′ consistsof a rotary encoder configured to detect a rotation angle θ₂′ of thedriven object 6′ as the position of the driven object.

The memory 9′ stores a lookup table indicating a relationship among arotation speed command value ω_(com)′, which is a speed command valuefor the motor 5′ to be input from the upper control device 17′ to themotor control device 10′, an actual rotation speed ω′ of the motor 5′corresponding to the position or speed of the motor 5′, which iscalculated in the same manner as the actual rotation speed ω of themotor 5, a q-axis current command value I_(qcom)′, and a d-axis currentcommand value I_(dcom)′.

The motor control device 10′ controls the motor 5′ driven by powerstored in the smoothing capacitor 3 connected to the three-phasealternating-current power source 1 via the converter 2. To do this, themotor control device 10′ samples each current value of three phases of aU-phase current I_(U)′, a V-phase current I_(V)′, and a W-phase currentI_(W)′ detected by current detection units 4 u′, 4 v′, and 4 w′ providedin the output lines of the inverter 4′ as a current value of the motor,and samples the rotation angles θ₁′ and θ₂′ as the position or speed ofthe motor and as the position or speed of the driven object,respectively. Then, the motor control device 10′ generates the PWMsignal V_(PWM)′ to drive the motor 5′ based on each of the sampledcurrent values of the U-phase current I_(U)′, the V-phase currentI_(V)′, and the W-phase current I_(W)′ and the sampled rotation anglesθ₁′ and θ₂′. The current detection units 4 u′, 4 v′, and 4 w′ consistof, for example, hole elements. Although power is supplied from thecontrol power source 11 to the motor control device 10′, the paththrough which power is supplied from the control power source 11 to themotor control device 10′ is omitted in FIG. 4 for simplification.Further, the motor control device 10′ carries out control to stop themotor 5′ when the power failure detection signal S_(s) is input from thepower failure detection unit 16 to the motor control device 10′ andcalculates reduction energy P_(d) stored in the smoothing capacitorwhile the motor 5′ is coming to a stop, based on the actual rotationspeed ω′ of the motor 5′. The speed reduction energy P_(d) is largerthan a stop operation power P_(sr2), to be explained later. Then, themotor control device 10′ provides information of the calculatedreduction energy P_(d) to the upper control device 17′.

In the system shown in FIG. 4, the memory 9′ and the motor controldevice 10′ are implemented by a processor including an input/outputport, a serial communication circuit, an A/D converter, a comparator,etc., and processing to control the motor 5′ is performed in accordancewith processing programs stored in a memory, not shown schematically.

In the system shown in FIG. 4, as will be explained later, the motorcontrol device 10 retracts the driven objects 6 and 6′ to a region wherethe driven objects 6 and 6′ do not interfere with an object when thethree-phase alternating-current power source 1 fails and the motorcontrol device 10′ stops the motor 5′ when the three-phasealternating-current power source 1 fails.

To do this, if the motor power source suppliable power P_(m) is equal toor less than retract operation power P_(sr1) as the first powernecessary to retract the driven object 6 and at the same time, is largerthan the stop operation power P_(sr2) as the second power necessary tostop the motor 5′, the sum of the motor power source suppliable powerP_(m) and the reduction energy P_(d) is larger than the sum of theretract operation power P_(sr1) and the stop operation power P_(sr2),and the control power source suppliable power P_(c) is smaller than thesum of the peripheral drive power P_(mf) and first motor control devicedrive power P_(mc1)′, to be explained later, when the three-phasealternating-current power source 1 fails, the power source supply stopunit 10 o in the motor control device 10 carries out control to stop thesupply of power from the control power source 11 to the monitor 12 andthe cooling fan 13 to lengthen the output hold time of the control powersource 11 by supplying the switching signal S_(off) to turn off theswitches 14 and 15 to the switches 14 and 15.

The upper control device 17′ consists of a CNC (computer numericalcontrol), etc., inputs the rotation speed command value ω_(com) tocontrol the motor control device 10 to the q-axis current command valuecreation unit 10 g and the d-axis current command value creation unit 10h in the motor control device 10, and inputs the rotation speed commandvalue ω_(com)′ to control the motor control device 10′ to a q-axiscurrent command value creation unit and a d-axis current command valuecreation unit (neither is shown schematically) in the motor controldevice 10. Further, the upper control device 17′ detects the voltage (DClink voltage) V_(c1) of the smoothing capacitor 3 and the voltage V_(c2)of the smoothing capacitor 11 b when the power failure detection signalS_(s) is input. Then, the upper control device 17′ calculates the motorpower source suppliable power P_(m) stored in the smoothing capacitor 3and the power stored in the smoothing capacitor 11 b, i.e., the controlpower source suppliable power P_(c) to which the control power source 11can supply when the alternating-current power source 1 fails,respectively, based on the detected voltage V_(c1) and the voltageV_(c2). Further, it may also be possible to establish serialcommunication between the motor control device 10, the motor controldevice 10′, and the upper control device 17′.

In the system shown in FIG. 4, the retract operation power P_(sr1) isstored in association with the rotation speed command value ω_(com) in amemory (not shown schematically) of the upper control device 17′ inadvance, and the stop operation power P_(sr2) is stored in associationwith the rotation speed command value ω_(com)′ in a memory (not shownschematically) of the upper control device 17′ in advance. Further, theperipheral drive power P_(mf) necessary to drive the monitor 12 and thecooling fan 13 when the alternating-current power source 1 fails isstored in the memory (not shown schematically) of the upper controldevice 17′ in advance. Furthermore, the first motor control device drivepower P_(mc1)′ necessary to drive the motor control devices 10 and 10′when the alternating-current power source 1 fails, second motor controldevice drive power P_(mc2)′ necessary to drive the motor control devices10 and 10′ at the time of increasing the above-mentioned sampling periodwhen the alternating-current power source 1 fails, and third motorcontrol device drive power P_(mc3)′ necessary to drive the motor controldevices 10 and 10′ at the time of increasing the sampling period and theabove-mentioned carrier frequency when the alternating-current powersource 1 fails, are stored in association with the rotation speedcommand value ω_(com) in the memory (not shown schematically) of theupper control device 17′ in advance.

For example, in the case where the motors 5 and 5′ are the firsthorizontal axis servo motor and the second horizontal axis servo motor,respectively, and the driven object 6 and the driven object 6′ are thetables of the same machine tool, the upper control device 17′ determineswhether or not the motors 5 and 5′ should be stopped in order to retractthe driven objects 6 and 6′ to a region where the driven objects 6 and6′ do not interfere with an object when the alternating-current powersource 1 fails, based on the rotation speed command values ω_(com) andω_(com)′.

For example, if the upper control device 17′ determines that the drivenobjects 6 and 6′ should be moved in the first horizontal direction (forexample, X-axis direction) in order to carry out the retract operationbut the driven objects 6 and 6′ do not have to be moved in the secondhorizontal direction (for example, Y-axis direction), the upper controldevice 17′ controls the motor control device 10 so as to drive the motor5 to retract the driven objects 6 and 6′, and controls the motor controldevice 10′ so as to stop the motor 5′.

Further, if the motor power source suppliable power P_(m) is larger thanthe retract operation power P_(sr1) and the control power sourcesuppliable power P_(c) is smaller than the sum of the peripheral drivepower P_(mf) and the first motor control device drive power P_(mc1) whenthe upper control device 17′ receives the power failure detection signalS_(s), the upper control device 17′ outputs the power supply stopcommand C_(p) to the power supply stop unit 10 o.

If the motor power source suppliable power P_(m) is equal to or lessthan the retract operation power P_(sr1) and at the same time, is largerthan the stop operation power P_(sr2), the sum of the motor power sourcesuppliable power P_(m) and the reduction energy P_(d) is larger than thesum of the retract operation power_(sr1) and the stop operation powerP_(sr2), and the control power source suppliable power P_(c) is smallerthan the sum of the peripheral drive power P_(mf) and the first motorcontrol device drive power P_(mc1) when the upper control device 17′receives the power failure detection signal S_(s), the upper controldevice 17′ also outputs the power supply stop command C_(p) to the powersupply stop unit 10 o.

If the motor power source suppliable power P_(m) is larger than theretract operation power P_(sr1), and the control power source suppliablepower P_(c) is smaller than the first motor control device drive powerP_(mc1) when the upper control device 17′ receives the power failuredetection signal S_(s), the upper control device 17′ outputs thesampling period increase command C_(s) to the current value samplingunit 10 a, the motor sampling unit 10 b, and the driven object samplingunit 10 c, respectively.

If the motor power source suppliable power P_(m) is equal to or lessthan the retract operation power P_(sr1) and at the same time, is largerthan the stop operation power P_(sr2), the sum of the motor power sourcesuppliable power P_(m) and the reduction energy P_(d) is larger than thesum of the retract operation power P_(sr1) and the stop operation powerP_(sr2), and the control power source suppliable power P_(c) is smallerthan the first motor control device drive power P_(mc1)′ when the uppercontrol device 17′ receives the power failure detection signal S_(s),the upper control device 17′ also outputs the sampling period increasecommand C_(s) to the current value sampling unit 10 a, the motorsampling unit 10 b, and the driven object sampling unit 10 c,respectively.

If the motor power source suppliable power P_(m) is control power sourcesuppliable power P_(c) is smaller than the second motor control devicedrive power P_(mc2)′ when the upper control device 17′ receives thepower failure detection signal S_(s), the upper control device 17′outputs the carrier frequency increase command C_(g) to the PWM signalgeneration unit 10 n.

If the motor power source suppliable power P_(m) is equal to or lessthan the retract operation power P_(sr1) and at the same time, is largerthan the stop operation power P_(sr2), the sum of the motor power sourcesuppliable power P_(m) and the reduction energy P_(d) is larger than thesum of the retract operation power P_(sr1) and the stop operation powerP_(sr2), and the control power source suppliable power P_(c) is smallerthan the second motor control device drive power P_(mc2)′ when the uppercontrol device 17′ receives the power failure detection signal S_(s),the upper control device 17′ also outputs the carrier frequency increasecommand C_(g) to the PWM signal generation unit 10 n.

If the motor power source suppliable power P_(m) is larger than theretract operation power P_(sr1), and the control power source suppliablepower P_(c) is smaller than the third motor control device drive powerP_(mc3)′ when the upper control device 17′ receives the power failuredetection signal S_(s), the upper control device 17′ outputs theoperation stop command C_(o) to the operation stop unit 10 p.

If the motor power source suppliable power P_(m) is equal to or lessthan the retract operation power P_(sr1) and at the same time, is largerthan the stop operation power P_(sr2), the sum of the motor power sourcesuppliable power P_(m) and the reduction energy P_(d) is larger than thesum of the retract operation power P_(sr1) and the stop operation powerP_(sr2), and the control power source suppliable power P_(c) is smallerthan the third motor control device drive power P_(mc3)′ when the uppercontrol device 17′ receives the power failure detection signal S_(s),the upper control device 17′ also outputs the operation stop commandC_(o) to the operation stop unit 10 p.

FIG. 5 is a flowchart of the operation of the upper control device inFIG. 4, which is performed at each control period (for example, 250microseconds) during the period from the start of the drive of the motor5 to the end of the drive of the motor 5 or the detection of the powerfailure of the three-phase alternating-current power source 1, and iscontrolled by processing programs executed in the upper control device17′. A case is explained where the motor 5 is driven in order to retractthe driven objects 6 and 6′ and at the same time, the motor 5′ isstopped.

In the flowchart in FIG. 5, after step S2 is completed, the uppercontrol device 17′ determines whether or not the motor power sourcesuppliable power P_(m) is larger than the retract operation powerP_(sr1) (step S21). If the motor power source suppliable power P_(m) isequal to or less than the retract operation power P_(sr1), the uppercontrol device 17′ determines whether or not the motor power sourcesuppliable power P_(m) is larger than the stop operation power P_(sr2)(step S22).

If the motor power source suppliable power P_(m) is equal to or lessthan the stop operation power P_(sr2), the processing flow is exited. Incontrast, if the motor power source suppliable power P_(m) is largerthan the stop operation power P_(sr2), the upper control device 17′determines whether or not the sum of the motor power source suppliablepower P_(m) and the reduction energy P_(d) is larger than the sum of theretract operation power P_(sr1) and the stop operation power P_(sr2) P(step S23). If the sum of the motor power source suppliable power P_(m)and the reduction energy P_(d) is equal to or less than the sum of theretract operation power P_(sr1) and the stop operation power P_(sr2),the processing flow is exited.

If it is determined that the motor power source suppliable power P_(m)is larger than the retract operation power P_(sr1) in step S21, or if itis determined that the sum of the motor power source suppliable powerP_(m) and the reduction energy P_(d) is larger than the sum of theretract operation power P_(sr1) and the stop operation power P_(sr2) instep S23, the upper control device 17′ determines whether or not thecontrol power source suppliable power P_(c) is equal to or more than thesum of the peripheral drive power P_(mf) and the first motor controldevice drive power P_(mc1)′ (step S24).

If the control power source suppliable power P_(c) is equal to or morethan the sum of the peripheral drive power P_(mf) and the first motorcontrol device drive power P_(mc1)′, the processing flow is exited. Incontrast, if the control power source suppliable power P_(c) is smallerthan the sum of the peripheral drive power P_(mf) and the first motorcontrol device drive power P_(mc1), the upper control device 17′ outputsthe power supply stop command C_(p) to the power supply stop unit 10 o(step S25).

After step S25 is completed, the upper control device 17′ determineswhether or not the control power source suppliable power P_(c) is equalto or more than the first motor control device drive power P_(mc1)′(step S26). If the control power source suppliable power P_(c) is equalto or more than the first motor control device drive power P_(mc1)′, theprocessing flow is exited. In contrast, if the control power sourcesuppliable power P_(c) is smaller than the first motor control devicedrive power P_(mc1)′, the upper control device 17′ outputs the samplingperiod increase command C_(s) to the current value sampling unit 10 a,the motor sampling unit 10 b, and the driven object sampling unit 10 c,respectively (step S27).

After step S27 is completed, the upper control device 17′ determineswhether or not the control power source suppliable power P_(c) is equalto or more than the second motor control device drive power P_(mc2)′(step S28). If the control power source suppliable power P_(c) is equalto or more than the second motor control device drive power P_(mc2)′,the processing flow is exited. In contrast, if the control power sourcesuppliable power P_(c) is smaller than the second motor control devicedrive power P_(mc2)′, the upper control device 17′ outputs the carrierfrequency increase command C_(g) to the PWM signal generation unit 10 n(step S29).

After step S29 is completed, the upper control device 17′ determineswhether or not the control power source suppliable power P_(c) is equalto or more than the third motor control device drive power P_(mc3)′(step S30). If the control power source suppliable power P_(c) is equalto or more than the third motor control device drive power P_(mc3)′, theprocessing flow is exited. In contrast, if the control power sourcesuppliable power P_(c) is smaller than the third motor control devicedrive power P_(mc3)′, the upper control device 17′ outputs the operationstop command C_(o) to the operation stop unit 10 p (step S31), and exitsthe processing flow.

If the motor power source suppliable power P_(m) is larger than the sumof the retract operation power P_(sr1) and the stop operation powerP_(sr2), the motor control device 10′ carries out control of the motor5′ in order to stop the motor 5′ when the processing flow in FIG. 5 ofthe upper control device 17′ is exited, and after the motor 5′ stops,the motor control device 10 carries out control of the motor 5 in orderto retract the driven object 6 to a region where the driven object 6does not interfere with an object.

In contrast, in the case where the motor 5 is a gravity axis servo motorand the motor 5′ is a main axis motor, and if the motor power sourcesuppliable power P_(m) is equal to or less than the sum of the retractoperation power P_(sr1) and the stop operation power P_(sr2), the motorcontrol device 10 carries out control of the motor 5 in order to retractthe driven object 6 to a region where the driven object 6 does notinterfere with an object when the processing flow in FIG. 5 of the uppercontrol device 17′ is exited or after the motor 5′ is stopped by themotor control device 10′. That is, in the case where it is necessary toretract the driven object 6 with priority over stopping the motor 5′,the control of the motor 5 in order to retract the driven object 6 iscarried out when the processing flow in FIG. 5 of the upper controldevice 17′ is exited, and in contrast, in the case where it is necessaryto stop the motor 5′ with priority over retracting the driven object 6,the control of the motor 5 in order to retract the driven object 6 iscarried out after the motor 5′ is stopped by the motor control device10′.

In the system shown in FIG. 4, if the motor power source suppliablepower P_(m) is equal to or less than the retract operation power P_(sr1)and at the same time, is larger than the stop operation power P_(sr2)the sum of the motor power source suppliable power P_(m) and thereduction energy P_(d) is larger than the sum of the retract operationpower P_(sr1) and the stop operation power P_(sr2), and the controlpower source suppliable power P_(c) is smaller than the sum of theperipheral drive power P_(mf) and the first motor control device drivepower P_(mc1)′ when the three-phase alternating-current power source 1fails, the supply of power from the control power source 11 to themonitor 12 and the cooling fan 13 is stopped, and therefore, it ispossible to decrease the power consumed by the motor control device 10.Consequently, even if the motor power source suppliable power P_(m) isequal to or less than the retract power P_(sr1), it is possible tolengthen the output hold time of the control power source 11 withoutincreasing the capacitance of the smoothing capacitor 11 b to make itpossible to perform the retract operation.

Further, if the motor power source suppliable power P_(m) is equal to orless than the retract operation power P_(sr1) and at the same time, islarger than the stop operation power P_(sr2), the sum of the motor powersource suppliable power P_(m) and the reduction energy P_(d) is largerthan the sum of the retract operation power P_(sr1) and the stopoperation power P_(sr2), and the control power source suppliable powerP_(c) is smaller than the first motor control device drive powerP_(mc1)′, the second motor control device drive power P_(mc2)′ or thethird motor control device drive power P_(mc3)′ when the three-phasealternating-current power source 1 fails, it is possible to furtherdecrease the power consumed by the motor control device 10 by increasingthe sampling period of the current value sampling unit 10 a, the motorsampling unit 10 b and the driven object sampling unit 10 c, byincreasing both the sampling period of the current value sampling unit,the motor sampling unit 10 b and the driven object sampling unit 10 cand the carrier frequency of the PWM signal V_(PWM)′ or by stopping theoperation of the driven object sampling unit 10 c.

The present invention is not limited to the above-mentioned embodimentsand can be modified and altered in a variety of ways. For example, it ispossible to use the motor control device according to the presentinvention in a machine other than the machine tool, in which it isnecessary to carry out a synchronized operation of a work and a tooltherein at all times.

Further, it is also possible to apply the motor control device accordingto the present invention to a case where full-closed control is notcarried out, and any one of the component, which consists of therotation angle detection unit 7, the motor sampling unit 10 b, thesubtracter 10 d, the filter 10 e and the adder 10 f and the component,which consists of the rotation angle detection unit 8, the driven objectsampling unit 10 c, the subtracter 10 d, the filter 10 e and the adder10 f, can be omitted.

Further, in the above-mentioned embodiments, the three-phasealternating-current power source 1 is used as an alternating-currentpower source, however, it is also possible to use a multi-phasealternating-current power source other than the three-phasealternating-current power source. It is also possible to apply the motorcontrol device according to the present invention to a system in whichpower source regeneration is performed. In this case, reactors arearranged between the three-phase alternating-current power source 1 andthe current detection units 1 u, 1 v, and 1 w and the converter 2 ismade to consist of a plurality of rectifier diodes and transistors inthe same number as that of the rectifier diodes.

Further, it is possible to make the rotation angle detection units 7 and8 consist of a part (for example, hole element or resolver) other thanthe rotary encoder. It is also possible to provide the motor samplingunit 10 b and the driven object sampling unit 10 c outside the motorcontrol device 10. Further, it is also possible to omit the rotationangle detection unit 7 and to calculate the rotation angle θ₁ and therotation speed ω₁ based on the alternating current and thealternating-current voltage supplied to the motor 5.

Further, the case where the monitor 12 and the cooling fan 13 are usedas peripherals is explained, however, it is also possible to use any oneof the monitor 12 and the cooling fan 13 or to use a peripheral otherthan the monitor 12 and the cooling fan 13.

Further, the case where the rotation angles θ₁ and θ₂ are sampled isexplained, however, it is also possible to sample the rotation speeds ω₁and ω₂ as the speed of the motor 5 and the speed of the driven object 6in place of the rotation angles θ₁ and θ₂ as the position of the motor 5and the position of the driven object 6.

Further, explanation is given on the assumption that the memory 9 is apart of the processor, however, it is also possible to configure thememory 9 as a part other than a processor. It is also possible toprovide the memory 9 within the q-axis current command value creationunit 10 g or within the d-axis current command value creation unit 10 h.

Further, the case where the power failure detection unit 16 detects thecurrent of the three-phase alternating-current power source 1 andcompares the level of the output signal corresponding to the detectedcurrent and the reference level is explained, however, it is alsopossible for the power failure detection unit 16 to detect the voltageof the three-phase alternating-current power source 1 and to compare thelevel of the output signal corresponding to the detected voltage withthe reference level.

Further, the case where the power failure detection unit 16 outputs thepower failure detection signal S_(s) to the upper control devices 17 and17′ is explained, however, it is also possible for the power failuredetection unit 16 to output the power failure detection signal S_(s) tothe q-axis current command value creation unit 10 g and to the d-axiscurrent command value creation unit 10 h and for the q-axis currentcommand value creation unit 10 g and the d-axis current command valuecreation unit 10 h to determine whether or not the power failure of thethree-phase alternating-current power source 1 is detected.

Further, the case where the sampling period (control period of the motorcontrol device 10) of the current value sampling unit 10 a, the motorsampling unit 10 b and the driven object sampling unit 10 c is doubledis explained, however, it is also possible to increase the samplingperiod to an arbitrary integer (three or more) multiple by performingsampling processing each time a clock signal output from a clock (notshown schematically) incorporated in the motor control device 10 isreceived an arbitrary number (three or more) of times. Further, it isalso possible to provide a clock control unit configured to increase thefrequency of the clock signal output from a clock (not shownschematically) incorporated in the motor control unit 10 to each unit ofthe motor control device 10 within the motor control device 10 in orderto increase the sampling period.

Further, the case where the carrier frequency of the PWM signal V_(PWM)is doubled is explained, however, it is also possible to increase thecarrier frequency of the PWM signal V_(PWM) to an arbitrary integer(three or more) multiple by setting a carrier frequency corresponding toan arbitrary number (three or more) of periods of a timer (not shownschematically) incorporated in the motor control device 10. Further, itis also possible to provide a timer control unit configured to increasethe count value of a timer (not shown schematically) incorporated in themotor control device 10 within the motor control device 10 in order toincrease the carrier frequency of the PWM signal V_(PWM).

Further, the case where processing to increase the sampling period ofthe current value sampling unit 10 a, the motor sampling unit 10 b andthe driven object sampling unit 10 c, processing to increase the carrierfrequency of the PWM signal V_(PWM), and processing to stop theoperation of the driven object sampling unit 10 c are performedsequentially in order to decrease the power consumed by the motorcontrol device 10, is explained, however, it is possible to stop theoperation of the driven object sampling unit 10 c before increasing thesampling period. Instead of performing all of the processing to increasethe sampling period, the processing to increase the carrier frequency,and the processing to stop the operation of the driven object samplingunit 10 c, it is also possible to perform only the processing toincrease the sampling period, or to perform both the processing toincrease the sampling period and the processing to increase the carrierfrequency, or to perform only the processing to stop the operation ofthe driven object sampling unit 10 c, or to perform both the processingto increase the sampling period and the processing to stop the operationof the driven object sampling unit 10 c.

Further, the case where the upper control devices 17 and 17′ detect thevoltage (DC link voltage) V_(c1) of the smoothing capacitor 3 and thevoltage V_(c2) of the smoothing capacitor 11 b and calculate the motorpower source suppliable power P_(m) and the control power sourcesuppliable power P_(c), is explained, however, it is also possible toprovide a first voltage detection unit configured to detect the voltage(DC link voltage) V_(c1) of the smoothing capacitor 3, a second voltagedetection unit configured to detect the voltage V_(c2) of the smoothingcapacitor 11 b, and a calculation unit configured to calculate the motorpower source suppliable power P_(m) and the control power sourcesuppliable power P_(c) in the motor control device 10.

Further, the case where the motor drive power P_(sr), the peripheraldrive power P_(mf), and the first motor control device drive powerP_(mc1), the second motor control device drive power P_(mc2) and thethird motor control device drive power P_(mc3) are stored in associationwith the rotation speed command value ω_(com) in the memory (not shownschematically) of the upper control devices 17 and 17′ in advance, isexplained, however, it is also possible to provide a storage unit, whichstores the motor drive power P_(sr), the peripheral drive power P_(mf),and the first motor control device drive power P_(mc1), the second motorcontrol device drive power P_(mc2) and the third motor control devicedrive power P_(mc3) in association with the rotation speed command valueω_(com), in the motor control device 10.

Furthermore, it is also possible to stop the operation of the motorsampling unit 10 b instead of stopping the operation of the drivenobject sampling unit 10 c in order to decrease the power consumed by themotor control device 10.

As above, the present invention is explained in relation to thepreferred embodiments thereof, however, it should be understood by aperson skilled in the art that various alterations and modifications canbe made without deviating from the scope disclosed by the claims.

The invention claimed is:
 1. A motor control device to which power issupplied from a control power source configured to supply power to aperipheral of a motor in order to control the motor driven by powerstored in a DC link part connected to an alternating-current powersource via a converter, the motor control device comprising: a currentvalue sampling unit configured to sample a current value of the motor; aPWM signal generation unit configured to generate a PWM signal to drivethe motor, based on the sampled current value of the motor; and a powersupply stop unit configured to stop supply of power from the controlpower source to the peripheral depending on the power stored in the DClink part and power to which the control power source can supply whenthe alternating-current power source fails, wherein the power supplystop unit stops the supply of power from the control power supply to theperipheral if the power stored in the DC link part is larger than anyone of first power necessary to retract an driven object connected tothe motor to a region where the driven object does not interfere with anobject, second power necessary to stop the motor in order to avoidinterference of the driven object connected to the motor with theobject, and the sum of the first power and the second power, and thepower to which the control power source can supply is smaller than thesum of power necessary to drive the peripheral and power necessary todrive the motor control device when the alternating-current power sourcefails.
 2. The motor control device according to claim 1, wherein thecurrent value sampling unit increases a sampling period of the currentvalue of the motor if the power stored in the DC link part is largerthan any one of the first power, the second power, and the sum of thefirst power and the second power, and the power to which the controlpower source can supply is smaller than the power necessary to drive themotor control device when the alternating-current power source fails. 3.The motor control device according to claim 2, wherein the PWM signalgeneration unit decreases a carrier frequency of the PWM signal if thepower stored in the DC link part is larger than any one of the firstpower, the second power, and the sum of the first power and the secondpower, and the power to which the control power source can supply issmaller than the power necessary to drive the motor control device whenthe alternating-current power source fails.
 4. The motor control deviceaccording to claim 1, further comprising: a motor sampling unitconfigured to sample the position or speed of the motor; a driven objectsampling unit configured to sample the position or speed of the drivenobject connected to the motor; and an operation stop unit configured tostop the operation of any one of the motor sampling unit and the drivenobject sampling unit if the power stored in the DC link part is largerthan any one of the first power, the second power, and the sum of thefirst power and the second power, and the power to which the controlpower source can supply is smaller than the power necessary to drive themotor control device when the alternating-current power source fails. 5.A motor control device to which power is supplied from a control powersource configured to supply power to a peripheral of a motor in order tocontrol the motor driven by power stored in a DC link part connected toan alternating-current power source via a converter, the motor controldevice comprising: a current value sampling unit configured to sample acurrent value of the motor; a PWM signal generation unit configured togenerate a PWM signal to drive the motor, based on the sampled currentvalue of the motor; and a power supply stop unit configured to stopsupply of power from the control power source to the peripheraldepending on the power stored in the DC link part and power to which thecontrol power source can supply when the alternating-current powersource fails, wherein the power supply stop unit stops the supply ofpower from the control power source to the peripheral if the powerstored in the DC link part is equal to or less than first powernecessary to retract the driven object connected to the motor to aregion where the driven object does not interfere with the object and atthe same time, is larger than second power necessary to stop anothermotor in order to avoid interference of a driven object connected to theother motor connected in parallel to the motor controlled by the motorcontrol device with an object, the sum of the power stored in the DClink part and reduction energy stored in the DC link part while theother motor is corning to a stop is larger than the sum of the firstpower and the second power, and the power to which the control powersource can supply is smaller than the sum of the power necessary todrive the peripheral and the power necessary to drive the motor controldevice and the motor control device of the other motor when thealternating-current power source fails.
 6. The motor control deviceaccording to claim 5, wherein the current value sampling unit increasesthe sampling period of the current value of the motor if the powerstored in the DC link part is equal to or less than the first power andat the same time, is larger than the second power, the sum of the powerstored in the DC link part and the reduction energy generated whileanother motor is coming to a stop is larger than the sum of the firstpower and the second power, and the power to which the control powersource can supply is smaller than the power necessary to drive the motorcontrol device and the motor control device of the other motor when thealternating-current power source fails.
 7. The motor control deviceaccording to claim 6, wherein the PWM signal generation unit decreasesthe carrier frequency of the PWM signal if the power stored in the DClink part is equal to or less than the first power and at the same time,is larger than the second power, the sum of the power stored in the DClink part and the reduction energy generated while another motor iscoming to a stop is larger than the sum of the first power and thesecond power, and the power that the control power source can supply issmaller than the power necessary to drive the motor control device andthe motor control device of the other motor when the alternating-currentpower source fails.
 8. The motor control device according to claim 5,further comprising: a motor sampling unit configured to sample theposition or speed of the motor; a driven object sampling unit configuredto sample the position or speed of the driven object connected to themotor; and an operation stop unit configured to stop the operation ofany one of the motor sampling unit and the driven object sampling unitif the power stored in the DC link part is equal to or less than thefirst power and at the same time, is larger than the second power, thesum of the power stored in the DC link part and the reduction energygenerated while another motor is coming to a stop is larger than the sumof the first power and the second power, and the power to which thecontrol power source can supply is smaller than the power necessary todrive the motor control device and the motor control device of the othermotor when the alternating-current power source fails.